The present invention relates to ferromagnetic thin film memories and more particularly to a process for the fabrication of a thin film magnetoresistive memory device.
The process for manufacturing the magnetoresistive bit lines involves depositing one or more layers of material over an underlying layer or surface, and etching the deposited material to a desired configuration of magnetic bits. Certain problems arise from the manufacturing process. A first problem is magnetic in nature and relates to the magnetic bit definition and specifically to the bit edge profile. In the past, a tungsten material has been used over the magnetic materials stack. The tungsten serves as a shorting connection between individual magnetic bits and the formation of a magnetic bit involves etching away some of the tungsten overlying a bit. Due to the etching process and the nature of the tungsten material, the bit edge profile exhibits a roughness and there may be some undercutting of the magnetic materials stack beneath the tungsten. The roughness and the undercutting may contribute to undesirable magnetic effects. The desired bit edge profile is a smooth edge with no undercutting.
A second problem relates to the control of contact resistance. In the past, the formation of a contact or connection to an underlying integrated circuit component in the semiconductor wafer included the opening of a contact and the depositing of the magnetic material stack within the contact. The presence of the magnetic materials within the contact can adversely affect the control of contact resistance.
Thus a need exists for a highly producible magnetoresistive random access memory process that provides a solution to the magnetic bit edge profile problems and the contact resistance problems of the past.